Microelectromechanical sensor and operating method for a microelectromechanical sensor

ABSTRACT

A microelectromechanical sensor and operating method therefor. The sensor has at least one movable electrode. An electrode arrangement is spaced apart from the movable electrode with a plurality of electrodes that can be driven separately and to which corresponding electrode signals can be applied that can be used to electrostatically set/change the application of force, the spring constant and the read-out factor of the movable electrode. An electrode signal generation unit is connected to the electrode arrangement and can be supplied with a force application signal, a spring constant signal and a read-out factor signal, which define the settings/changes to be brought about with regard to the application of force, spring constant and read-out factor of the movable electrode. The electrode signal generation unit generates each electrode signal in a manner dependent on the force application signal, the spring constant signal and the read-out factor signal and matches the electrode signals to one another so that the application of force, the spring constant and the read-out factor of the movable electrode can be set/changed to specific desired values independently of one another.

The invention relates to a microelectromechanical sensor and to an operating method for such a sensor.

Microelectromechanical sensors form the basis of many technical products. Microelectromechanical sensors have proved to be worthwhile for example in the field of navigation, where they are used as Coriolis gyroscopes. The functioning of a microelectromechanical sensor will be explained below by way of example on the basis of a Coriolis gyroscope.

Coriolis gyroscopes have a mass system that can be caused to effect oscillations. The mass system generally has a multiplicity of oscillation modes which are initially independent of one another. In the operating state of the Coriolis gyroscope (that is to say in the operating state of the microelectromechanical sensor), a specific oscillation mode of the mass system is excited artificially, which mode is referred to hereinafter as “excitation oscillation”. If the Coriolis gyroscope is rotated, Coriolis forces occur which draw energy from the excitation oscillation of the mass system and transfer it to a further oscillation mode of the mass system, this mode being referred to hereinafter as “read-out oscillation”. In order to determine rotations of the Coriolis gyroscope, the read-out oscillation is tapped off and a corresponding read-out signal is examined in respect of whether changes in the amplitude of the read-out oscillation, which represent a measure of the rotation of the Coriolis gyroscope, have occurred. Coriolis gyroscopes can be realized either as an open-loop system or as a closed-loop system. In a closed-loop system, the amplitude of the read-out oscillation is continuously reset to a fixed value—preferably zero—by means of respective control loops, and the resetting forces are measured.

The mass system (which is also referred to hereinafter as “resonator”) of the Coriolis gyroscope (more generally: of the microelectromechanical sensor) can in this case be configured in a variety of ways. By way of example, it is possible to use a mass system embodied in one piece. As an alternative, it is possible to divide the mass system into two oscillators, which are coupled to one another via a spring system and can perform relative movements with respect to one another.

A known embodiment of a Coriolis gyroscope 20 is indicated schematically in FIG. 1. The Coriolis gyroscope 20 has a charge amplifier 1, an analog-to-digital converter 2, a signal separation 3, demodulators 4, 5, a control system 6, a modulator 7, drivers 8, 9, a resonator 10 and an electrode system 11 having four electrodes 11 ₁ to 11 ₄.

The resonator 10 can be excited to effect oscillations by means of the electrodes 11 ₁ to 11 ₄. Furthermore, the spring constant of the resonator 10 can be electrostatically set or changed by means of electrodes 11 ₁ to 11 ₄. The movement of the resonator 10 is determined by measuring a charge transfer Δq on an electrode provided on the resonator 10 (“movable center electrode”), which is brought about by the movement of the resonator 10 within the electrostatic field generated by the electrodes 11 ₁ to 11 ₄. A signal S₇ proportional to the charge transfer is output by the charge amplifier 1 to the analog-to-digital converter 2 and converted by the latter into a corresponding digital signal S₈, which is fed to the signal separation 3. From this signal, signals S₃ to S₆ are generated with the aid of the demodulators 4, 5, the control system 6 and the modulator 7 and the drivers 8, 9, which signals are applied to the electrodes 11 ₁ to 11 ₄ and ensure that the deflections of the resonator 10 that are brought about by Coriolis forces are compensated for. For the precise functioning of the Coriolis gyroscope 20, reference should be made for example to the patent specification DE 103 20 675.

The object on which the invention is based is to specify a microelectromechanical sensor, for example a capacitive sensor or a piezoelectric sensor, which has a functionality that is as extensive as possible despite a small number of sensor electrodes.

In order to achieve this object, the invention provides a microelectromechanical sensor in accordance with patent claim 1. Furthermore, the invention provides an operating method for a microelectromechanical sensor in accordance with patent claim 11. Preferred configurations and developments of the concept of the invention are found in the dependent claims.

The invention provides a microelectromechanical sensor, comprising:

-   -   at least one movable electrode,     -   an electrode arrangement spaced apart from the movable electrode         and having a plurality of electrodes which can be driven         separately and to which corresponding electrode signals can be         applied, wherein the electrode signals can be used to         electrostatically set/change the application of force, the         spring constant and the read-out factor of the movable         electrode,     -   an electrode signal generation unit, which is connected to the         electrode arrangement and can be supplied with a force         application signal, a spring constant signal and a read-out         factor signal, which define the settings and/or changes to be         brought about with regard to the application of force, spring         constant and read-out factor of the movable electrode,     -   wherein the electrode signal generation unit generates each         electrode signal in a manner dependent on the force application         signal, the spring constant signal and the read-out factor         signal and matches the electrode signals to one another in such         a way that the application of force, the spring constant and the         read-out factor of the movable electrode can be set and/or         changed to specific desired values independently of one another.

An essential insight on which the invention is based is that the electrode signals for any desired electrode arrangement can be matched to one another in such a way that the application of force, the spring constant and the read-out factor of the movable electrode can be set/changed to specific desired values independently of one another, thereby affording a maximum flexibility of the operating method of the microelectromechanical sensor. In this context, “any desired electrode arrangement” means any desired spatial arrangement of at least three electrodes.

As already mentioned, the mass system (which is also referred to hereinafter as “resonator”) of the microelectromechanical sensor can be configured in a variety of ways. By way of example, it is possible to use a mass system embodied in one piece. As an alternative, it is possible to divide the mass system into two oscillators, which are coupled to one another via a spring system and can perform relative movements with respect to one another.

In one embodiment, the sensor according to the invention is provided with a charge transfer unit, which detects charge transfers occurring on the movable electrode, wherein the instantaneous movement of the movable electrode can be determined by means of an evaluation unit, on the basis of the detected charge transfer.

In one embodiment, the electrode signal generation unit generates each electrode signal in a manner dependent on the force application signal, the spring constant signal and the read-out factor signal in such a way that the charge transfer detected on the movable electrode only contains charge transfer components which originate from the movement of the movable electrode and from the value of the read-out factor; in this case, the read-out factor should be interpreted as a gain factor for reading out the movement of the movable electrode.

The electrode arrangement can comprise an even or odd number of electrodes. Furthermore, the dimensions and configurations of the individual electrodes can differ among one another. In one preferred embodiment, the electrode arrangement contains four (preferably identical) electrodes which can be grouped for example into two electrode pairs, wherein the electrodes are configured axially symmetrically with respect to a first axis, which separates the two electrode pairs from one another, and axially symmetrically with respect to a second axis, which separates the electrodes of the respective electrode pairs among one another. In an advantageous manner, the movable electrode is configured centrosymmetrically with respect to the point of intersection of the two axes of symmetry.

In an embodiment in which the movable electrode is embodied as part of a resonator, the movable electrode can be excited to effect oscillations and the sensor can be used for example as a Coriolis gyroscope.

In an embodiment comprising two movable electrodes, two electrode arrangements and two electrode signal generation units, both movable electrodes can be read separately from one another by a corresponding choice of the two read-out factors and the movements (influenced by means of the application of force) and spring constants can be set independently of one another.

The invention furthermore provides an operating method for a microelectromechanical sensor having a movable electrode and an electrode arrangement spaced apart from the movable electrode and having a plurality of electrodes which can be driven separately and to which corresponding electrode signals can be applied, comprising the following steps:

-   -   generation of the electrode signals in a manner dependent on a         force application signal, a spring constant signal and a         read-out factor signal, which define the settings and/or changes         to be effected with regard to the movement, spring constant and         read-out factor of the movable electrode,     -   application of the electrode signals to the corresponding         electrodes in order to electrostatically set and/or change the         application of force, the spring constant and the read-out         factor of the movable electrode,     -   wherein each electrode signal is generated in a manner dependent         on the force application signal, the spring constant signal and         the read-out factor signal and the electrode signals are matched         to one another in such a way that the application of force, the         spring constant and the read-out factor of the movable electrode         are set and/or changed to specific desired values independently         of one another.

The invention is explained in more detail below in exemplary embodiment with reference to the figures, in which:

FIG. 1 shows a basic schematic diagram of a known microelectromechanical sensor (Coriolis gyroscope),

FIG. 2 shows an embodiment of a microelectromechanical sensor according to the invention with one movable electrode,

FIG. 3 a shows a further embodiment of a microelectromechanical sensor according to the invention with two movable electrodes,

FIG. 3 b shows a schematic time characteristic for the application of two read-out factors.

FIG. 2 shows an excerpt from a preferred embodiment of the microelectromechanical sensor 30 according to the invention. The excerpt shown in FIG. 2 can be compared approximately with the “ensemble” of modulator 7, drivers 8, 9, resonator 10 and electrode arrangement 11 ₁ to 11 ₄ in FIG. 1.

FIG. 2 shows an electrode arrangement 31 spaced apart in relation to a movable electrode 29, which can be for example part of a resonator (not shown), said electrode arrangement comprising a first to fourth electrode 31 ₁ to 31 ₄. The first and third electrodes 31 ₁, 31 ₃, and the second and fourth electrodes 31 ₂, 31 ₄, respectively form an electrode pair. The electrodes of an electrode pair are arranged axially symmetrically with respect to an axis A. Furthermore, the electrode pairs are separated from one another axially symmetrically in relation to one another by an axis D perpendicular to the axis A. The movable electrode 29 is configured for example centrosymmetrically with respect to a point of intersection S of the two axes of symmetry A, B, as shown in FIG. 2.

An electrode signal generation unit 32 can furthermore be seen, which can be supplied with a force application signal S₂₀ (also designated as “f”), a spring constant signal S₂₁ (also designated as “Δω”), and a read-out factor signal S₂₂ (also designated as “m”). The read-out factor signal S₂₂ is squared in a squaring unit 33 and the signal S₂₃ thus obtained is fed with a negative sign to a first addition stage 34, where said signal is added to the spring constant signal S₂₁. The output signal S₂₄ of the addition stage 34 is fed to a second and to a third addition stage 35, 36. In the second addition stage 35, the signal S₂₄ is added to the signal S₂₀, whereas in the third addition stage 36, the signal S₂₀ with a negative sign is added to the signal S₂₄. The output signals S₂₅, S₂₆ of the addition stages 35, 36 are fed to root units 37, 38, which respectively determine the root from one of the signals S₂₅, S₂₆. The output signals S₂₇, S₂₈ of the root units 37, 38 are fed to a fourth to seventh addition stage 39 to 42, by which each of the signals S₂₇, S₂₈ is in each case added to the signal S₂₂ once and subtracted from said signal once. Corresponding output signals S₂₉ to S₃₂ are fed to digital-to-analog converters 43 to 46, which convert the (hitherto digital) signals into analog signals u_(o1), u_(o2), u_(u1), u_(u2) and apply them to the corresponding electrodes 31 ₁ to 31 ₄. The signals u_(o1), u_(o2), u_(u1) and u_(u2) represent the electrode signals in the sense of the invention and can be expressed as follows depending on the force application signal S₂₀ (=f), the spring constant signal S₂₁ (=Δω) and the read-out factor signal S₂₂ (=m):

u _(o1)=√{square root over (Δω−m ² +f)}+m  (1)

u _(o2)=−√{square root over (Δω−m ² +f)}+m  (2)

u _(u1)=√{square root over (Δω−m ² −f)}−m  (3)

u _(u2)=−√{square root over (Δω−m ² −f)}−m  (4)

Accordingly, the electrode signals u_(o1), u_(o2) represent those electrode signals which are present at the electrodes 31 ₁, 31 ₂ situated above the axis A, and u_(u1), u_(u2) represent the electrode signals which are present at the electrodes 31 ₃, 31 ₄ situated below the axis A. The connection of the movable electrode 29 is at virtual ground; the charge flowing from the movable electrode 29 is measured.

FIG. 3 shows how two movable, electrically connected electrodes 29, 50 can be combined in the multiplex method. The control signals m₁ and m₂, switched in the manner illustrated in FIG. 3 b, alternately make a respective movable electrode 29, 50 visible to the charge amplifier 70. The force impressions f₁ and f₂ and the matchings Δω₁ and Δω₂ can be chosen independently thereof.

FIG. 3 shows an electrode arrangement 51 spaced apart in relation to a second movable electrode 50, which is electrically connected to the at least one movable electrode 29, said electrode arrangement comprising a first to fourth electrode 51 ₁ to 51 ₄. The first and third electrodes 51 ₁, 51 ₃, and the second and fourth electrodes 51 ₂, 51 ₄, respectively form an electrode pair. The electrodes of an electrode pair are arranged axially symmetrically with respect to an axis A₂. Furthermore, the electrode pairs are separated from one another axially symmetrically relative to one another by an axis D₂ perpendicular to the axis A₂.

A second electrode signal generation unit 52 can furthermore be seen, which can be supplied with a second force application signal S₂₀ (also designated as “f₂”), a second spring constant signal S₂₁ (also designated as “Δω₂”), and a second read-out factor signal S₂₂ (also designated as “m₂”). The second read-out factor signal S₂₂ is squared in a second squaring unit 53 and the signal S₂₃ thus obtained is fed with a negative sign to an eighth addition stage 54, where said signal is added to the second spring constant signal S₂₁ . The output signal S₂₄ of the eighth addition stage 54 is fed to a ninth and to a tenth addition stage 55, 56. In the ninth addition stage 55, the signal S₂₄ is added to the signal S₂₀ , whereas in the tenth addition stage 56, the signal S₂₀ with a negative sign is added to the signal S₂₄ . The output signals S₂₅ , S₂₆ of the addition stages 55, 56 are fed to second root units 57, 58, which respectively determine the root from one of the signals S₂₅ , S₂₆ . The output signals S₂₇ , S₂₈ of the second root units 57, 58 are fed to an eleventh to fourteenth addition stage 59 to 62, by which each of the signals S₂₇ , S₂₈ is in each case added to the signal S₂₂ once and subtracted from said signal once. Corresponding output signals S₂₉ to S₃₂ are fed to second digital-to-analog converters 63 to 66, which convert the (hitherto digital) signals into analog signals u_(o1) , u_(o2) , u_(u1) , u_(u2) and apply them to the corresponding electrodes 51 ₁ to 51 ₄. The signals u_(o1) , u_(o2) , u_(u1) , and u_(u2) represent the electrode signals in the sense of the invention and can be expressed as follows depending on the second force application signal S₂₀ , the second spring constant signal S₂₁ and the second read-out factor signal S₂₂ :

u _(o1) =√{square root over (Δω₂ −m ₂ ² +f ₂)}+m ₂  (5)

u _(o2) =−√{square root over (Δω₂ −m ₂ ² +f ₂)}+m ₂  (6)

u _(u1) =√{square root over (Δω−m₂ ² −f ₂)}−m ₂  (7)

u _(u2) =−√{square root over (Δω−m₂ ² −f ₂)}−m ₂  (8)

Accordingly, the electrode signals u_(o1) , u_(o2) represent those electrode signals which are present at the electrodes 51 ₁, 51 ₂ situated above the axis A₂, and u_(o1) , u_(u2) represent the electrode signals which are present at the electrodes 51 ₃, 51 ₄ situated below the axis A₂.

Further aspects of the invention will be explained in the description below.

It is advantageous if the following requirements can be met during the operation of (capacitive) microelectromechanical sensors for measuring acceleration or rate of rotation:

-   1. A defined electrostatically generated force is intended to be     able to be exerted on a movable electrode (torquer function). -   2. A defined electrostatically generated spring force is intended to     be able to be applied to the same movable electrode. The spring     constant is generally negative and is intended to make a positive     mechanical spring “softer” to a predetermined extent in order thus     to enable a defined tuning of the natural resonance of a mechanical     oscillator. -   3. The deflection of the electrode is intended to be able to be made     measurable by means of a read-out factor that can be set (pick-off     function). -   4. One intention is for it to be possible, during operation, for the     measurement signal not to contain any further components than those     dependent on the deflection and the read-out factor.

Suppose that a capacitor having a movable electrode is provided. The electrode can be moved by a deflection x at an actuation point. The capacitance is then dependent on x: C=C(x). It follows from the energy theorem that in the case of a voltage U applied to the capacitor at the actuation point an electrostatic force

$\begin{matrix} {F = {\frac{U^{2\;}}{2}\frac{C}{x}}} & (9) \end{matrix}$

takes effect. The differential capacitor was two capacitors with a common actuation point, wherein

C ₁(x)=C ₂(−x)  (10)

holds true. It is then the case that approximately:

C ₁(x)=C ₀(1+α₁ x+α ₂ x ²)  (11)

and thus

C ₂(x)=C ₀(1−α₁ x+α ₂ x ²)  (12)

If the voltages U₁ and U₂ are then present at the capacitors, the force at the actuation point of the movable electrode becomes:

$\begin{matrix} {F = {{\frac{U_{1}^{2}}{2}\frac{C_{1}}{x}} + {\frac{U_{2}^{2}}{2}\frac{C_{1}}{x}}}} & (13) \end{matrix}$

Substituting (11) and (12) yields:

F=(U ₁ ² −U ₂ ²)α₁ C ₀2x(U ₁ ² +U ₂ ²)α₂ C ₀  (14)

Consequently, the force is composed of a part that is independent of x and a portion that is proportional to x and corresponds to a spring constant. The part independent of x is proportional to U₁ ²−U₂ ², and the spring constant is proportional to U₁ ²+U₂ ².

In the case of four capacitors where

C _(o1)(x)=C _(o2)(x)=C _(o)(1+α₁ x+α ₂ x ²)  (15)

C _(u1)(x)=C _(u2)(x)=C _(u)(1−α₁ x+α ₂ x ²)  (16)

the following correspondingly holds true for the force:

F=(U _(o1) ² +U _(o2) ² −U _(u1) ² −U _(u2) ²)α₁ C ₀2x(U _(o1) ² −U _(o2) ² −U _(u1) ² −U _(u2) ²)α₂ C ₀  (17)

Here, therefore, the distance-independent term is proportional to

U_(o1) ²U_(o2) ²−U_(u1) ²−U_(u2) ²  (18)

and the spring constant is proportional to

U_(o1) ²U_(o2) ²+U_(u1) ²+U_(u2) ²  (19)

The distance-independent part is suitable for impressing a desired force (resetting, torquer), and the spring constant, in interaction with a spring-mass system, enables the tuning of the latter to a desired resonant frequency.

The following holds true for the charges:

Q=C _(o1) U _(o1) +C _(o2) U _(o2) +C _(u1) U _(u1) +C _(u2) U _(u2)  (20)

Substituting (15) and (16), and disregarding the quadratic term, yields:

Q=2C ₀(U _(o1) +U _(o2) +U _(u1) +U _(u2))  (21)

+2C₀(U_(o1)+U_(o2)−U_(u1)−U_(u2))α₁x  (22)

The first term generates a crosstalk independent of x (and is generally undesirable), while the second part is proportional to x, and is therefore suitable for reading out the deflection x. If the quadratic term is taken into account, then

Q==2C ₀(U _(o1) U _(o2) +U _(u1) +U _(u2))(1+α₂ x ²)  (23)

+2C₀(U_(o1)+U_(o2)−U_(u2))α₁x  (24)

and it vanishes together with the constant term (if the crosstalk is made zero, that is to say for U_(o1)+U_(o2)+U_(u1)+U_(u2)=0).

Requirements 1.)-3.) can be met independently of one another with the sensor according to the invention and the sensor according to the invention. It is therefore possible both for a force to be able to be applied without a read-out signal being generated and, conversely, for a read-out factor different than zero, no applied force having to be the necessary consequence.

For general electrode arrangements it is possible to establish analogous systems to the equations if the following rules are taken into account:

The charges on all the electrodes always have a magnitude such that

1) in total at the charge amplifier input there are no terms independent of the deflection x, 2) in total at the charge amplifier input there is a part dependent on the deflection x and having a gain factor that can be set, 3) there is a force effect that can be set, independently of the deflection x, on the movable electrode, 4) there is an electrostatic spring that can be set in terms of its spring constant at the movable electrode.

The read-out factor that can be set can be used to realize e.g. a “down-converting detector” if for example the read-out factor is configured as a sinusoidal carrier having the same frequency as the electrode oscillation. In this case, the oscillation is down-converted to the frequency 0, which leads to a phase-sensitive demodulator. Furthermore, by means of the read-out factor that can be set, the read-out function of a plurality of oscillators whose movable electrodes are electrically connected can be read out in the time division multiplex method by a procedure in which it is always the case that only the read-out factor of one oscillator is set to a value different than zero and accordingly it is always the case that only one oscillator movement is detected by the common charge amplifier in temporal succession. The read-out function

$\begin{matrix} {{Q\left( {\Delta \; x} \right)} = {U\left( {C_{0} + {\frac{\partial C}{\partial x}\Delta \; x}} \right)}} & (25) \end{matrix}$

based on a capacitance measurement quite generally has the effect that when the read-out factor is switched on by means of the voltage U, not only a component dependent on the deflection Δx occurs, but additionally at the same time a considerably larger portion dependent on the quiescent capacitance C₀. The method according to the invention suppresses this undesirable portion, as is shown below on the basis of the nomenclature in FIG. 2.

The force acting on the movable electrode 29, according to equation (18) is proportional to

u _(o1) ²+_(o2) ² −u _(u1) ² −u _(u2) ²=4f  (26)

Requirement 1 is thus met. The detuning on account of an electrostatic spring, according to equation (19) is proportional to

u _(o1) ² +u _(o2) ² +u _(u1) ² +u _(u2) ²=4ΔΩ  (27)

Requirement 2 is thus met. The read-out factor, according to equation (21) is proportional to

u _(o1) +u _(o2) −u _(u1) −u _(u2)=4m  (28)

The 3rd requirement is thus met. Furthermore, according to equation (22),

u _(o1) +u _(o2) +u _(u1) +u _(u2)=0  (29)

whereby, finally, the 4th requirement is met. For a correct function, the dimensioning must be performed such that always

|f|<Δω−m ²  (30)

The invention accordingly describes an operating method for microelectromechanical sensors (MEMS sensors) with split electrodes. The method according to the invention allows excitation force, resonance tuning and read-out factor to be set separately from one another in systems comprising a plurality of electrically coupled movable electrodes. A read-out process during multiplex operation is thus possible totally independently of excitation processes (generation of the excitation oscillation) and tuning processes (e.g. frequency tuning of excitation oscillation to read-out oscillation in order to obtain a double-resonant resonator). 

1. A microelectromechanical sensor, comprising: at least one movable electrode, an electrode arrangement spaced apart from the movable electrode and having a plurality of electrodes which can be driven separately and to which corresponding electrode signals can be applied, wherein the electrode signals can be used to electrostatically set/change the application of force, the spring constant and the read-out factor of the resonator, an electrode signal generation unit, which is connected to the electrode arrangement and can be supplied with a force application signal, a spring constant signal and a read-out factor signal, which define the settings/changes to be brought about with regard to the application of force, spring constant and read-out factor of the movable electrode, wherein the electrode signal generation unit generates each electrode signal in a manner dependent on the force application signal, the spring constant signal and the read-out factor signal and matches the electrode signals to one another in such a way that the application of force, the spring constant and the read-out factor of the resonator can be set/changed to specific desired values independently of one another.
 2. The microelectromechanical sensor as claimed in claim 1, characterized by a charge transfer unit, which detects charge transfers occurring on the movable electrode, and an evaluation unit, which determines the instantaneous movement of the movable electrode on the basis of the detected charge transfer.
 3. The microelectromechanical sensor as claimed in claim 2, characterized in that the electrode signal generation unit generates each electrode signal in a manner dependent on the force application signal, the spring constant signal and the read-out factor signal in such a way that the charge transfer only contains charge transfer components which originate from the movement of the movable electrode and from the value of the read-out factor.
 4. The microelectromechanical sensor as claimed in claim 1, characterized in that the electrode arrangement contains four electrodes.
 5. The microelectromechanical sensor as claimed in claim 4, characterized in that the four electrodes are grouped into two electrode pairs, wherein the electrodes are configured axially symmetrically with respect to a first axis, which separates the two electrode pairs, from one another, and axially symmetrically with respect to a second axis, which separates the electrodes of the respective electrode pairs among one another.
 6. The microelectromechanical sensor as claimed in claim 5, characterized in that the movable electrode is configured centrosymmetrically with respect to the point of intersection of the two axes of symmetry.
 7. The microelectromechanical sensor as claimed in claim 5, characterized in that the electrode signals are given by the following equations: u _(o1)=√{square root over (Δω−m ² +f)}+m u _(o2)=−√{square root over (Δω−m ² +f)}+m u _(u1)=√{square root over (Δω−m ² −f)}−m u _(u2)=−√{square root over (Δω−m ² −f)}−m where (Δω) represents the value of the spring constant signal, (m) represents the value of the read-out factor signal, and (f) represents the value of the force application signal, (u_(o1), u_(o2)) represent the values of the electrode signals lying above the second axis, and (u_(u1), u_(u2)) represent the values of the electrode signals lying below the second axis.
 8. The microelectromechanical sensor as claimed in claim 7, characterized in that the following relation holds true: |f|<Δω−m ²
 9. The microelectromechanical sensor as claimed in claim 1, characterized in that the movable electrode is embodied as part of a resonator.
 10. The microelectromechanical sensor as claimed in claim 1, characterized by a second movable electrode, which is electrically connected to the at least one movable electrode, a second electrode arrangement spaced apart from the second movable electrode and having a further plurality of electrodes which can be driven separately and to which corresponding electrode signals can be applied, wherein the electrode signals can be used to electrostatically set/change the application of force, the spring constant and the read-out factor of the second movable electrode, a second electrode signal generation unit, which is connected to the second electrode arrangement and can be supplied with a second force application signal, a second spring constant signal and a second read-out factor signal, which define the settings/changes to be brought about with regard to the application of force, spring constant and read-out factor of the resonator, wherein the second electrode signal generation unit generates each electrode signal in a manner dependent on the second force application signal, the second spring constant signal and the second read-out factor signal and matches the electrode signals to one another in such a way that the second application of force, the second spring constant and the second read-out factor of the second movable electrode can be set/changed to specific desired values independently of one another and independently of the application of force, the spring constant and the read-out factor of the at least one movable electrode.
 11. An operating method for a microelectromechanical sensor having at least one movable electrode and an electrode arrangement spaced apart from the movable electrode and having a plurality of electrodes which can be driven separately and to which corresponding electrode signals can be applied, comprising the following steps: generation of the electrode signals in a manner dependent on a force application signal, a spring constant signal and a read-out factor signal, which define the settings/changes to be effected with regard to the application of force, spring constant and read-out factor of the movable electrode, application of the electrode signals to the corresponding electrodes in order to electrostatically set/change the application of force, the spring constant and the read-out factor of the movable electrode, wherein each electrode signal is generated in a manner dependent on the force application signal, the spring constant signal and the read-out factor signal and the electrode signals are matched to one another in such a way that the application of force, the spring constant and the read-out factor of the movable electrode are set/changed to specific desired values independently of one another. 